The invention relates to the protection of threads on rods or bolts which will be subjected to extreme corrosion or other damaging attack. In particular, the invention includes a releaseable telescoping device which is useful in the protection of threads on each anchor rods against corrosion. The corrosion is largely due to electrolysis. Due to a larger surface area for corrosion created by threads, and due to the peaks or ridges associated therewith, stronger electric potentials are created at the location of the threads than at other points on the rod. The stronger electric potentials plus the inherent difficulty of protecting threaded surfaces causes more rapid and destructive corrosion to areas of the anchor rod which are threaded than those which are not threaded. By completely insulating the rod and thus eliminating the possibility of an electric current between soils of different chemical compositions through the rod, electrolysis (the major cause of corrosion) is prevented.